1. Field of the Invention
The present principles relate generally to video encoding and decoding and, more particularly, to methods and apparatus for example-based data pruning using intra-frame patch similarity.
2. Background Information
Data pruning is a video preprocessing technology that achieves better video coding efficiency by removing part of the input video data before the input video data is encoded. The removed video data is recovered at the decoder side by inferring the removed video data from the decoded data. One example of data pruning is image line removal, which removes some of the horizontal and vertical scan lines in the input video.
In a first approach, a new data pruning method called example-based data pruning is employed, in which external videos or video frames that have been previously transmitted to the decoder side are used to train an example patch library. The patch library is then used to prune and recover the video data.
There have been several efforts to explore using data pruning to increase compression efficiency. For example, in a second approach and a third approach, a texture replacement based method is used to remove texture regions at the encoder side, and re-synthesize the texture regions at the decoder side. Compression efficiency is gained because only synthesis parameters are sent to the decoder, which are smaller than the regular transformation coefficients. In a fourth approach and a fifth approach, spatio-temporal texture synthesis and edge-based inpainting are used to remove some of the regions at the encoder side, and the removed content is recovered at the decoder side, with the help of metadata such as region masks. However, the fourth and fifth approaches need to modify the encoder and decoder so that the encoder/decoder can selectively perform encoding/decoding for some of the regions using the region masks. Therefore, it is not exactly an out-of-loop approach (i.e., the encoder and decoder need to be modified). In a sixth approach, a line removal based method is proposed to restate a video to a smaller size by selectively removing some of the horizontal or vertical lines in the video with a least-square minimization framework. The sixth approach is an out-of-loop approach, and does not require modification of the encoder/decoder. However, completely removing certain horizontal and vertical lines may result in loss of information or details for some videos.
Some preliminary research on data pruning for video compression has been conducted. For example, in a seventh approach, a data pruning scheme using sampling-based super-resolution is presented. The full resolution frame is sampled into several smaller-sized frames, therefore reducing the spatial size of the original video. At the decoder side, the high-resolution frame is re-synthesized from the downsampled frames with the help of metadata received from the encoder side. In an eighth approach, an example-based super-resolution based method for data pruning is presented. A representative patch library is trained from the original video. Afterwards, the video is downsized to a smaller size. The downsized video and the patch library are sent to the decoder side. The recovery process at the decoder side super-resolves the downsized video by example-based super-resolution using the patch library. However because there is substantial redundancy between the patch library and downsized frames, it has been discovered that it may be difficult to achieve compression gain using the eighth approach.
In the aforementioned first approach, an example-based data pruning method creates a patch library using the video frames that have been sent to the decoder side and uses the patch library to prune and recover video frames. However, this method does not consider the intra-frame patch dependency, which may happen if there are repetitive textures or patterns in a video frame.
In the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) Moving Picture Experts Group-4 (MPEG-4) Part 10 Advanced Video Coding (AVC) Standard/International Telecommunication Union, Telecommunication Sector (ITU-T) H.264 Recommendation (hereinafter the “MPEG-4 AVC Standard”), intra-frame block prediction is realized by block prediction from the neighboring blocks. However, long-range similarity of non-neighboring blocks is not exploited to increase compression efficiency.
These and other drawbacks and disadvantages of these approaches are addressed by the present principles, which are directed to methods and apparatus for example-based data pruning using intra-frame patch similarity.